1. Field of the Invention
This invention relates to a locking prevention apparatus consisting of a split ring of substantially rigid material that engages circumferentially the locking shaft connecting the interior door knob of a passage lock assembly to the adjacent interior face plate to limit translational motion of the interior door knob along the locking shaft toward the interior face plate and thereby prevent accidental or unintentional locking of the door.
2. Description of the Prior Art
Interior rooms of buildings frequently have passage doors containing a passage lock door knob assembly in which the exterior door knob can be rotated to open and close the door but can not be actuated to lock the door, while the interior door knob assembly can be used to open and close the door as well as to lock the door from the interior of the room by sliding the interior door knob along the shaft connecting the interior door knob to the interior face plate of the door knob assembly and rotating the interior door knob to lock the door. Such passage lock assemblies are susceptible to the problem that the door can easily be locked accidently or unintentionally by an adult or by a child.
The prior art discloses several types of apparatus adapted to prevent opening, closing or unlocking of doors. For example, U.S. Pat. No. 2,786,706 discloses a rotatable latch engagement member retained in a normally inoperative position by a biasing force supplied by opposing springs mounted on opposite sides of the door between the door knobs and the face plates of the latch assembly. That apparatus maintains the latch assembly in an inoperative position; however, that condition can be readily overcome by urging the latching assembly into operation by either pulling or pushing on one of the door knobs. That apparatus merely increases the force necessary to operate the latch assembly but does not prevent locking of the latch assembly.
U.S. Pat. No. 2,883,850 discloses an apparatus adapted to prevent unlocking or opening of an exterior door, which apparatus includes a cylindrical casing which encloses the interior door knob and is secured in place by a yoke member which passes through slots in the cylindrical casing and is secured against removal by a conventional padlock. That apparatus permits locking of the door from the outside.
U.S. Pat. No. 3,980,328 discloses an apparatus which prevents unlocking a door from the outside, which apparatus includes a rigid door bar mounted across the exterior surface of the door and connected to the door jam. The door bar includes a yoke-like holding member which engages the shaft of the outside door knob and is tightened against the door bar by three fasteners, thereby squeezing the door knob between the yoke-like holding member and the door bar to prevent turning of the door knob. That apparatus does not disclose means to prevent unintentional locking of a door that remains in condition for normal passage use.
U.S. Pat. No. 3,084,965 discloses a cup shaped door knob guard which prevents children from opening doors by reaching the door knob from below. The top portion of the guard is open to permit operation of the door knob from above. That apparatus does not prevent accidental or unintentional operation and locking of the door knob assembly by persons other than small children. In addition, attachment of that apparatus requires at least partial disassembly of the door knob assembly.
U.S. Pat. No. 4,007,956 discloses an anti-theft device that prevents unlocking of an exterior door having a key actuated locking mechanism. That device is adapted to assure that normal operation of the locking and unlocking functions can be performed in the normal manner. Installation of that device requires disassembly of the door knob assembly.
There remains a need for a simply constructed, easily installed or removed, lock prevention apparatus for passage lock assemblies on interior doors.